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References: <20230323025003.94447-1-songmuchun@bytedance.com>
In-Reply-To: <20230323025003.94447-1-songmuchun@bytedance.com>
From:   Marco Elver <elver@google.com>
Date:   Thu, 23 Mar 2023 09:28:01 +0100
Message-ID: <CANpmjNP+WU4AjmNLMz317ipDKr2BQ-zJrNkJeqqAFiPwcYOs4g@mail.gmail.com>
Subject: Re: [PATCH] mm: kfence: fix handling discontiguous page
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     glider@google.com, dvyukov@google.com, akpm@linux-foundation.org,
        jannh@google.com, sjpark@amazon.de, muchun.song@linux.dev,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
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On Thu, 23 Mar 2023 at 03:50, 'Muchun Song' via kasan-dev
<kasan-dev@googlegroups.com> wrote:
>
> The struct pages could be discontiguous when the kfence pool is allocated
> via alloc_contig_pages() with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP.
> So, the iteration should use nth_page().
>
> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Reviewed-by: Marco Elver <elver@google.com>

> ---
>  mm/kfence/core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kfence/core.c b/mm/kfence/core.c
> index d66092dd187c..1065e0568d05 100644
> --- a/mm/kfence/core.c
> +++ b/mm/kfence/core.c
> @@ -556,7 +556,7 @@ static unsigned long kfence_init_pool(void)
>          * enters __slab_free() slow-path.
>          */
>         for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
> -               struct slab *slab = page_slab(&pages[i]);
> +               struct slab *slab = page_slab(nth_page(pages, i));
>
>                 if (!i || (i % 2))
>                         continue;
> @@ -602,7 +602,7 @@ static unsigned long kfence_init_pool(void)
>
>  reset_slab:
>         for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
> -               struct slab *slab = page_slab(&pages[i]);
> +               struct slab *slab = page_slab(nth_page(pages, i));
>
>                 if (!i || (i % 2))
>                         continue;
> --
> 2.11.0
>
> --
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